It is generally well known, in the art, that the access doors on passenger transit railway vehicles, such as subway cars and the like, are provided with individual automatic door operators which function to open and close each door or pair of doors so that passengers can have access to and from the vehicle. All automatic door operators are normally activated in unison by a door opening and closing control mechanism at the hand of the vehicle operator. Typically, such an automatic door operator is driven by a hydraulic or pneumatic cylinder or an electric motor, which is connected to an overhead linkage or driving mechanism adapted to open and close the door or doors in response to the reciprocating action of the hydraulic or pneumatic cylinder rod or the rotating action of the electric motor.
It is sometimes necessary, however, to isolate a given door from its associated automatic door operator in order to keep the door in the closed position when the other doors are opened to permit passengers to ingress or egress. For example, a particular door operator mechanism may be faulty, or some other safety considerations may require that passengers not have access through a given particular door for any one of a number of reasons. Prior art techniques for isolating an access door usually involve a time consuming and complex effort of disconnecting of the door from the automatic door operator, and locking the door in place. Normally, a door so disconnected and locked in the closed position, cannot be opened by the emergency door opening mechanism, which can lead to a hazardous condition.